render multi-line document properly

[eZioPan]

and some clippy fix.

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will need a

• [ ] Accept embassy-rs/chiptool#31
• [ ] Rebase to remove my fork from codebase.

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This PR doesn't change function of stm32-data-gen, so there should be no change in ci diff.

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BELOW IS OUT OF DATE, SEE embassy-rs/chiptool#31 INSTEAD

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Render metapac document from one-line to multi-line.

eg.

from

#[doc = "Scaling factor. Input value has been multiplied by 2^(-n) before for argument. Output value will need to be multiplied by 2^n later for results."]

to

#[doc = "Scaling factor.  "]
#[doc = "Input value has been multiplied by 2^(-n) before for argument.  "]
#[doc = "Output value will need to be multiplied by 2^n later for results."]

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[embassy-ci[bot]]

diff: https://ci.embassy.dev/jobs/31abfdc41613/artifacts/diff.html